Condensation product of cinchona bark alkaloids with thiuram sulphides



Patented Aug. 15, 1933 UNITED, STATES CONDENSATION PRODUCT or CINCHONA BARK ALKALOIDS WITH PHIDES THIURAM SUL- Ralph E. Lawrence, Wicklifie, Ohio, assignor to The Grasselli Chemical Company, Cleveland, Ohio, a Corporation of Delaware No Drawing. Original application December 19, 1931, Serial No. 582,186. Divided and this application November 22, 1932. Serial No. 643,952

. 4 Claims.

The present invention relates to novel organic compounds and their use for controlling the action of acids upon metals, and to processes of cleaning, pickling, scaling or removing oxides,

5 scale and any other undesirable incrustations from metal articles, and theinvention comprises the condensation products obtained by heating together a cinchona bark alkaloid with a thiuram sulphide and the use of such products as inhibitors.

Thiuram sulphides are chemical compounds of the general formula in which R stands for hydrogen or ahydrocarbon radical and a: for the numerals 1, 2, 3, etc.

I found that when thiuram sulphides and cinchona bark alkaloids are mixed and the mixture heated to temperatures above about 100 C,

a chemical reaction takes place with evolution of heat. I have been unable to isolate from the reaction mixtures any definite chemical compound. Even When 'using' other than stoichiometric proportions, I did not succeed in separating any of the two original products from the reaction product. When using quinoidine, which is itself a complex, amorphous mixture of various unknown products, as the cinchona bark alkaloid, no such stoichiometric proportion-could be calculated.

As far as physical and inhibiting properties are concerned, there is no substantial difference in the product obtained by using varying amounts of the two ingredients. I have produced icondensation products from mixtures containing from 10 to 50% by weight of the thiuram sulphide compound, although in my preferred process I use about 25%.

Among the various components from which I can produce my novel inhibitors, I prefer both tute for they thiuram sulphides the dithiocarbamates from which the thiuram sulphides are produced by oxidation and obtain substantially the same condensation products. I may assume that under the conditions of the reaction the thiuram sulphides are formed at an intermediate stage and then react with the alkaloid.

The preferred process for preparing quinoidine condensation products is as follows: The quinoidine is first melted in any suitable receptacle until it is in a fluid state. A definite amount of thiuram sulphide of the general formula,

is then added and stirred into the molten quinoidine. Heating of the mass is continued until a temperature of about 130 C. is reached. This temperature is held for about 15-20 minutes, after which the product is allowed to cool.

The condensation products of cinchona bark alkaloids with thiuram sulphides are amorphous, resinous products of yellowish-to brown color. They have no definite melting point; They are substantially insoluble in aqueous caustic alkali.

The condensation products prepared from quinine and quinidine are soluble in the common organic solvents. Those prepared from quinoidine and tetramethyl-thiuram mono and disulphide are only little soluble in common organic solvents except acetone and chloroform in which they are easily soluble.

These novel condensation products are almost completely soluble in dilute mineral acids.

The usual pickling and cleaning baths for metallic articles consist of dilute, non-oxidizing mineral acids,- such as sulphuric, hydrochloric, and acetic acids. The articles are treated therewith at various temperatures and under conditions best suited to the particular problem, it being understood that pickling of sheet steel, steel stock for wire, etc., for instance, may require different operations, concentrations of acid, temperature, etc., than descaling boiler tubes or freeing water pipes from rust and other undesirable incrustations.

The addition of a small amount of a cinchona bark alkaloid-thiuram sulphide condensation product to the acids used in such operations will prevent or greatly reduce the attack of the acid on the metal itself, without materially affecting the dissolution of the scale, rust and other incrustations. This results in a noticeable saving of acid, but the main advantage of the use of my novel inhibitors is the protection of the metal articles which are not weakened or pitted by continued action of the acid after removal of the scale, rust, and other incrustations.

Amounts less than k of 1% of my novel condensation product are usually suflicient to produce the desired inhibiting effect. Among the various thiuram sulphides used in the preparation of my quinoidine condensation product, I found 'Ibtra methylthiuram monthat some of the best for the preparation of my condensation product are the tetraalkyl-thiuram disulphides and the tetra-alkaylthiuram monosulphides. V

In pickling operations the concentration of acid in the pickling bath varies from to and the temperature from 140 to 190 F. Laboratory tests by the so-called loss in weight method;

which consists of a beaker-scale pickling opera- Concentration of compound inhibitor Period of pickling 1 2 i 3 l' 2 a Time of pickling (minutes) 1 Scale included Yes Inhibitor Condensation product of:

Quinoidine 75% Tetra metl1ylthiu sulphide Condensation product of:

Quinoidine V Tetra methylthiuram 79. 5% 00. 4% 80.9% 97. 0% 06. 0%

monosulphide 25%- 7 quinoidine only.; Tetra methyl thiuram disul- V phide only sulhpide only I In the above table the efficiency for the first period includes the loss in weight due to adhering scale and other incrustationswhich .vary on ,the

" different specimens of steel. {In the second and thirdlpe riods' the lossis due to loss-0f bare metal onlyr Similar results are obtained with condensation products from other cinchona bark alkaloids and other thiuram sulphides.

I am aware that both types of materials from which my novel condensation products are produced have been patented as inhibitors. See United States Patents 1,742,986, Jan. 7, 1930, H. P. Corson and 1,809,621, June 9, 1931, H. P. Cor- S011.

The results described above clearly show the superior efliciency of the condensation products over the individual compounds from which these products are obtained. In addition, the condensation products are much easier soluble in the dilute pickling acids than the thiuram sulphides.

This is a division of my application Ser. No.

582,186, filed Dec. 19, 1931.

I claim: V

1. As a new compound a condensation product of a cinchona bark alkaloid with a thiuram sulphide which is an amorphous yellow to brown substance, insoluble in aqueous caustic alkali, almost completely-soluble in dilute acid and has the property of inhibiting the action of acids upon metals.

2. As a new product a condensation product of quinoidine with a'tetramethyhthiuram sulphide which is an amorphous yellowish-brown, resinous substanceinsoluble in aqueous caustic alkali, soluble in acetone and chloroform, almost completely soluble in dilute mineral acid and has the property of inhibiting the action of acids upon metals. r

3. The process of making a condensation product of a cinchona bark alkaloid and a thiuram sulphide which comprises mixing the two and heating them to an elevated temperature.

4; The process of making a condensation prod-- uct of quinoidine and tetrar'nethyl-thiuram sulphide which comprises melting quinoidine, adding to the melt tetram'ethyl-thiuram sulphide and heating the mixture to a temperature above 100 C.

I RALPH E. LAWRENCE. 

